A week after being the victim of racist abuse by Bastia fans, Mario Balotelli sealed a straightforward win to lift Nice above Monaco with 49 points from 22 games.
Monaco will return to the top if they avoid defeat at champions Paris St Germain later on Sunday.
Alassane Plea put the hosts ahead after a fine one-two with Valentin Eysseric in the 11th minute.
Jean Seri doubled the lead after being set up by Vincent Koziello seven minutes before the break.
Former France international Jimmy Briand reduced the arrears in the 63rd minute with an angled shot, but Balotelli wrapped it up for Nice three minutes from fulltime after collecting a through ball from Arnaud Souquet.
(Reporting by Julien Pretot; Editing by Toby Davis)